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Re: [dm-devel] [PATCH] multipath: better check for daemon mode.



On Wed, Aug 31, 2011 at 09:46:32PM -0500, Benjamin Marzinski wrote:
> Christophe, would it be possible to get this merged?

Is there some objection to merging this?  It's not just a cosmetic
change.  For multipath devices added via ev_add_map(), disassemble_map()
will be called before the waiter thread is started, and this check will
allow any unknown paths in the device to be stored.  However, paths
added this way never get properly setup like they do when they are added
via ev_add_path(), or at configuration time.

So say you had a multipath device, "mpatha", which should include the
path "sda", except that the path was mistakenly blacklisted. If you
unblacklist the path and then run multipath, without first reconfiguring
multipathd, it will segfault, since it adds sda, but never initializes
all the necessary information.

We could solve this problem by making sure that paths added through
disassemble_map() go through the same initialization code that paths
added through ev_add_path(), but I don't see the necessity. If
multipathd isn't monitoring a path, it's either because that path was
blacklisted, or because that path was manually removed.  While it's
possible to create a multipath device using blacklisted paths via
dmsetup, multipathd still shouldn't be monitoring those paths.  The same
goes with paths that were manually removed via the multipathd command
line interface.

And if, for some reason, multipathd wasn't monitoring a path it should
be, the best thing to do is to reconfigure multipathd.  Code that
watched multipath.conf and automatically reconfigured multipathd when it
changed would be a nice addition though.

Thanks,
-Ben

> Thanks,
> -Ben
> 
> On Mon, Jul 25, 2011 at 01:47:52PM -0500, Benjamin Marzinski wrote:
> > Switching to conf->daemon to check if we are in daemon mode.
> > 
> > Signed-off-by: Benjamin Marzinski <bmarzins redhat com>
> > ---
> >  libmultipath/dmparser.c |    3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > Index: multipath-tools-110713/libmultipath/dmparser.c
> > ===================================================================
> > --- multipath-tools-110713.orig/libmultipath/dmparser.c
> > +++ multipath-tools-110713/libmultipath/dmparser.c
> > @@ -13,6 +13,7 @@
> >  #include "structs.h"
> >  #include "util.h"
> >  #include "debug.h"
> > +#include "config.h"
> >  
> >  #define WORD_SIZE 64
> >  
> > @@ -330,7 +331,7 @@ disassemble_map (vector pathvec, char * 
> >  				strncpy(pp->dev_t, word, BLK_DEV_SIZE);
> >  
> >  				/* Only call this in multipath client mode */
> > -				if (!mpp->waiter && store_path(pathvec, pp))
> > +				if (!conf->daemon && store_path(pathvec, pp))
> >  					goto out1;
> >  			}
> >  			FREE(word);
> > 
> > --
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> > dm-devel redhat com
> > https://www.redhat.com/mailman/listinfo/dm-devel
> 
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